In 3rd Generation Partnership Project (3GPP) Long Term Evolution (LTE) mobile networks, there exist often unwanted small coverage islands (e.g., overshootings from neighboring cells), so called “hot spots”, which offer a very-confined lower path loss within the coverage of another (surrounding) cell due to topological peculiarities. A User Equipment (UE), which is moving towards a hot spot, is ordered by the serving cell to execute an handover towards that hot spot when the required handover conditions are fulfilled and the configured handover event is reported by the UE.
An handover requires a significant amount of signalling between Evolved Universal Terrestrial Radio Access Network (E-UTRAN) NodeBs (eNBs) over the X2 or S1 interface, and between UEs and eNBs over the air interface. Handovers towards unwanted hot spots should be avoided if the available signal quality of the current serving cell is still good enough within the hot spot area, that is to say the requested service(s) can still be supported by the current serving cell even if the hot spot offers a better radio quality.
Handover and radio link failure rates shall be minimised by self-optimisation of handover parameters or by avoidance of handovers towards inappropriate cells.
It is the task for an efficient mobile network like LTE to analyze handovers towards hot spots and to block unnecessary handovers. In current wireless systems like 3GPP UMTS, 3GPP2 CDMA2000, or IEEE 802.16 (WIMAX) networks, this is achieved via costly drive tests. In LTE, this shall be carried out automatically by means of Self-Organizing Networks (SON).
3GPP Radio Access Network (RAN) Working Group 2 (WG2) is currently investigating UE measurements for drive test minimisation. These measurements will be sent to eNBs and/or to operation and maintenance centres (O&M) for further processing. Self-optimisation of handover parameters is currently under discussion in 3GPP RAN WG3, which can be based inter alia on reported UE measurements.